Benzo[g]pyrido[2,1-b]-quinazolinones

ABSTRACT

Disclosed are novel benzo[g]Pyrido[2,1-b]-quinazolinones which are active as anti-allergy agents and thus have utility in the treatment of allergic reactions such as bronchial asthma.

This application is a continuation-in-part of U.S. Patent Application Ser. No. 614,399, filed Sept. 18, 1975, which is now U.S. Pat. No. 4,012,387.

The present invention relates to compounds of the following generic series: ##STR1## where R₁ and R₂ are selected from the group consisting of hydrogen, carboxyalkyl, carboxamido, cyano, or 5-tetrazolyl. Alkyl as used above refers to straight or branched chained radicals of 1 to 4 carbons in length. The pharmaceutical salts of these compounds are also within the scope of this invention.

The preferred compounds are those structural species wherein R₁ and R₂ are hydrogen or 5-tetrazolyl and in which only one tetrazolyl function appears in the generic structure at any one time.

The compounds of this invention may be prepared by the chemical routes in patent application Ser. No. 614,399, the disclosure of which is incorporated herein.

The following examples are given for a more complete understanding of the invention:

EXAMPLE 1 ##STR2## Ethyl 6-oxo-6H-benzo[g]pyrido[2,1-b]quinazoline-3-carboxylate.

A mixture of 3-amino-2-naphthoic acid (30.0 g, 160 mmol), 6-chloronicotinic acid (25.2 g, 160 mmol) and 750 ml of ethanolic hydrogen chloride was heated at reflux for 72 hrs. The reaction mixture was cooled to 0° and the solid collected by filtration to give the hydrochloride salt; 29.6 g, mp 352°-5° dec. The salt was suspended in aqueous ammonia and filtered to give the crude base which yielded the analytically pure ester upon recrystallization from pyridine; yield, 9.1 g (20%), mp 235°-38° dec.

Anal. (C₁₉ H₁₄ N₂ O₃) CHN satisfactory.

EXAMPLE 2 ##STR3## 6-Oxo-6H-benzo[g]pyrido[2,1-b]quinazoline-3-carboxamide.

A mixture of 6-chloronicotinamide (16.75 g, 107 mmol), 3-amino-2-naphthoic acid (20.0 g, 107 mmol) and glacial acetic acid (200 ml) was heated at reflux for 24 hrs. The resulting suspension was cooled to room temperature and filtered to give 8.70 g (28.0%) of the crude product, mp 325°-40° dec. One recrystallization from pyridine gave the analytical material, mp 242°-248° dec.

Anal. (C₁₇ H₁₁ N₃ O₂) CHN satisfactory.

EXAMPLE 3 ##STR4## 3-Cyano-6-oxo-6H-benzo[g]pyrido[2,1-b]quinazoline.

A reaction mixture containing 3.03 g (10.0 mmol) of 6-oxo-6H-benzo[g]pyrido[2,1-b]quinazoline-3-carboxamide, 2.86 g (15.0 mmol) of p-toluenesulfonyl chloride, 70 ml of DMF and 250 ml of pyridine was heated at 110° for 78 hrs. The resultant orange suspension was cooled and poured onto 1.5 l. ice-H₂ O and acidified with conc. HC1. The solid which formed was collected to give 2.60 g (93.2%) of crude nitrile product, mp 355°-58° dec. One recrystallization of the crude nitrile from pyridine gave 2.05 g (73.5%) of the analytically pure nitrile, mp 354°-56° dec.

Anal. (C₁₇ H₉ N₃ O) CHN satisfactory.

EXAMPLE 4 ##STR5## 6-Oxo-6H-3-(5-tetrazolyl)-benzo[g]pyrido[2,1-b]quinazoline.

A DMF solution (250 ml) containing 0.68 g (10.5 mmol) NaN₃, 0.62 g (10.5 mmol) NH₄ Cl and 1.0 g (3.68 mmol) of 3-cyano-6-oxo-6H-benzo[g]pyrido[2,1-b]quinazoline was heated at 110° for 32 hrs. The reaction mixture was poured into 1 l. H₂ O, acidified with conc. HCl and extracted with CHCl₃ (2 × 1.5 l.). The combine CHCl₃ extracts were dried (MgSO₄) and evaporated to give 0.80 g (69.0%) of crude tetrazolyl product; mp 278°-88° dec. One recrystallization of the crude product from pyridine gave the analytical material; yield, 0.40 g (34.5%), mp 295°-302° dec.

Anal. (C₁₇ H₁₀ N₆ O) CHN satisfactory.

Compounds of this invention have been found to reduce allergic responses to antigen challenge by inhibiting antibody-antigen reactions in mammals such as rats, when tested in accordance with the procedure of Herzig [Immunopharmacology, M. E. Rosenthale and H. C. Mansmann, Eds., John Wiley and Son, N.Y., 1975]. Following this protocol, the table below shows comparative data between the effectiveness of the compound according to Example 1 and Intal (Chromoglycate) which is presently the commercial compound of choice for use in allergic bronchial asthma.

                                      TABLE I                                      __________________________________________________________________________     Effective dose 50% inhibition rat passive cutaneous anaphylaxis test           (ED.sub.50 -PCA)                                                               __________________________________________________________________________                                        ED.sub.50 -PCA(rat)                                                            ip.  iv.  po.                               __________________________________________________________________________     Example 4                          Active                                                                              Active                                                                              Active                            Intal                                                                           ##STR6##                          inactive                                                                            Active                                                                              inactive                          __________________________________________________________________________

As can be seen, the Example 4 compound is active when given orally or intraperitonially, whereas the commercial compound is not. Furthermore, when compared for i.v. administration, the novel compound has been found to be ten to fifteen times as effective as the commercial compound. 

We claim:
 1. A compound of the structure: ##STR7## wherein R₁ and R₂ are selected from the group consisting of hydrogen and tetrazolyl with the proviso that R₁ and R₂ are not identical and its pharmaceutically acceptable salts.
 2. The compound of claim 1 which is 3-(1H-tetrazol-5-yl)-6H-benzo[g]pyrido[2,1-b]-quinazolin-6-one.
 3. The compound of claim 1 which is 1-(1H-tetrazol-5-yl)-6H-benzo[g]pyrido[2,1-b]-quinazolin-6-one. 